There is significant worldwide interest in carbon nanotubes (multi walled, double walled, single walled). Nanotubes are known to be composed either of a single sheet, in which case they are called single-walled nanotubes (SWNTs), or made up from several concentric sheets, when they are called multi-walled nanotubes (MWNTs). Carbon nanotubes can be formed from petroleum-based sources or form biological-based sources.
However, there are concerns with ease of handling and processing. One approach to address this is to deliver carbon nanotubes encapsulated in a resin matrix. Since the carbon nanotubes are not free, but encapsulated, handling is improved. And since carbon nanotubes are already dispersed to varying degrees, subsequent dispersion in a resultant polymer composition should be more efficient.
In addition, demand and applications for electrically conductive plastics and plastics with modified mechanical properties have grown. In these uses, one seeks to exploit the unique properties of plastics, often as an alternative to metals. For example, electrically conductive polymeric materials are desirable for many applications including coatings for the dissipation of electrostatic charge from electrical parts, and the shielding of electrical components to prevent interference by electromagnetic waves. Enhanced electrical conductivity in polymer materials enables coating by electrostatic spray painting. The primary methods of increasing the electrical conductivity of plastics have been to fill them with conductive additives such as metallic powders, metallic fibers, intrinsically conductive polymeric powder, e.g., polypyrrole, or carbon black. The most common method involves carbon black. However, each of these approaches has some shortcomings. Metallic fiber and powder enhanced plastics have diminished mechanical strength. Further, cost is high and their density makes high weight loadings necessary. Intrinsically conductive polymers have high costs and are often not stable in air. Thus, their use is frequently impractical. It has been recognized that the addition of carbon nanotubes to polymers in quantities less than that of carbon black can be used to produce conductive end products and/or to modify the mechanical properties of the product.
Encapsulation of carbon nanotubes is known. Multi-walled carbon nanotubes (MWCNT's) are marketed as nanotubes compounded in a resin matrix. The resin matrix is formed depending upon customer needs. For example, if the customer is interested in compounding MWCNT's into polyamide-6, a resin matrix of carbon nanotubes in polyamide-6 is prepared. The MWCNT's concentration in such matrixes typically ranges from approximately 2% to approximately 20%. These matrices are called master batches. This process requires a distinct master batch for each end use. Such a process is costly and inefficient.